Any fitting of a new grip safety will require you to refinish the receiver.
When the Colt grip safety is removed there is a segment of the frame's palm web area that requires removal. The radius of the S&A safety is .250".
Once the jig is installed, the excess frame material becomes evident.
This is Fenrir with the first few file passes made to the frame.
Note the black finish on the jig rounds. As you get closer to the finished radius you will start to notice the file starting to remove the black finish, (Your getting close when that happens.)
After fitting and function testing the parts were taped and put in the sand-blaster.
The final product;
This is the before photo. See how the grip safety points back and down.
This is the after photo. A true high-ride beavertail!